1. Field of the Invention
The present invention relates to an optical recording/reproducing apparatus, and particularly, to an optical recording/reproducing apparatus capable of adjusting a skew of an optical pickup within a range that the optical pickup can accurately recognize an optical disc.
2. Description of the Background Art
Recently, mobile communication devices such as a personal information terminal, a picture phone or the like have been generalized according to development of a multimedia environment, popularization of a personal computer and generalization of a data transmission network and advancement of a wireless communication technology. Such generalization of mobile communication devices has brought about a considerable increase in a capacity of information to be processed and stored in those devices.
In order to cope with the situation, researches are ongoing to increase a record density of an optical recording medium such as a CD or a DVD, in crease a resolution of an optical pickup unit and implement small optical components.
Since the advent of an early optical recording/reproducing apparatus for a CD-ROM, an optical disc has been improved to obtain a rapid access speed and high density and as a result, a large capacity of optical disc has been developed, which can reproduce simple information and also can record information.
An optical recording/reproducing apparatus for recording and reproducing an optical disc requires a high level of signal processing techniques. Especially, reducing a slant error, that is, a skew error between an optical axis of an optical pickup and the optical disc is required as a core technique for accomplishing accuracy in recording/reproducing information.
In the optical recording/reproducing apparatus requiring the advanced signal processing technique, if a skew error occurs since an optical beam of the optical pickup is not accurately made incident vertically on a signal record face of the optical disc, that is, if a skew error occurs, a signal is distorted and thus the signal cannot be accurately processed.
Because a fine assembly error occurs due to a tolerance of the optical disc and smoothness of a mounting surface of a spindle motor installed at a base plate supporting the optical pickup, even after the optical pickup is assembled at the base plate, adjustment of a skew of an optical pickup (adjustment of a tilt of an optical pickup) should be necessarily performed.
In order to reduce a skew, development of an optical pickup skew adjustment unit capable of mechanically adjusting the optical pickup skew adjustment unit is considered as the most effective way to improve a signal processing performance.
FIG. 1 is a plane view showing a conventional optical recording/reproducing apparatus.
As shown in FIG. 1, a conventional optical recording/reproducing apparatus 1 includes a spindle motor 20 installed on a base plate 10, a turn table 40 rotatably installed on the spindle motor 20, for mounting an optical disc 30 thereon; an optical pickup 50 installed on the base plate 10, for irradiating an optical beam irradiated from an optical system (not shown) to a surface of the optical disc 30; a main shaft 60 installed on the blase plate 10, for supporting one side of the optical pickup; a sub-shaft 70 positioned parallel with the main shaft 60 at a certain distance therebetween and installed on the blase plate 10, for supporting the other side of the optical pickup 50.
Arms 51 are respectively formed at both sides of the optical pickup 50 in order to couple the optical pickup 50 itself to the main shaft 61 and the sub-shaft 70.
Skew adjustment units 80 for adjusting a skew are respectively installed at both ends of the sub-shaft 70 and one end of the main shaft 60, and a fixing unit 90 is installed at the other end of the main shaft 60.
In the skew adjustment unit 80, a support portion 82 having a spring 81 is formed on the base plate 10, a screw hole 82a is formed at an upper portion of the support portion 82, and a skew adjustment screw 83 is threaded to the screw hole 82a. 
One end of the main shaft 60 is inserted in an insertion hole 82b formed at the side of the support portion 82 and supported by the spring 81. The other end of the main shaft 60 is rotatably coupled to a fixing unit 90 by a hinge 91.
When the optical recording/reproducing apparatus constructed as above adjusts a skew of the optical pickup 50, one of the four ends of the main shaft 60 and the sub-shaft 70 is set as a standard, and the skew adjustment screw 83 is rotated to adjust the height, so that an optical axis (S) is accurately vertically made incident to the optical disc 40 and thus a skew is corrected.
However, in the conventional optical recording/reproducing apparatus, if the skew adjustment screw 93 is excessively rotated, a distance (D) between the optical disc 30 and the optical pickup 50 becomes too far. Namely, the optical pickup 50 is so distanced from the optical disc 30 that the optical pickup 50 goes beyond its operation range. Then, the optical pickup 50 cannot read a signal of the optical disc 30 accurately.